The present invention relates to a process and an apparatus for the quasi-continuous or continuous chemical conversion of materials, and in particular to a process and an apparatus for the conversion of waste cellulose to glucose by acid hydrolyzation.
Acid hydrolysis of cellulose has been extensively studied for the better part of the century, particularly in connection with the manufacturing of ethanol from wood wastes. It has long been known that cellulose can be hydrolyzed in acid solutions and converted to its monomer, glucose, and the reaction has been experimentally investigated since this discovery. The reaction results from the fact that the monomers of cellulose are in anhydroglucose units, and that during hydrolyzation, a water ion is added to the cellulose monomer unit to obtain the heavier molecular weight glucose.
Recently, there has been a growing interest in the utilization of waste cellulose for energy production, because of the possibility of producing ethyl alcohol from glucose, and for the purposes of materials recovery.
While the acid hydrolysis of cellulose is heterogeneous, it can be regarded as a homogeneous reaction, provided that the cellulose reactant is dispersed in the form of fine particles, i.e., 200-mesh or less. The kinetically predicted sugar yields assume that the cellulose reactant has appropriate chemical reactivity for the acid hydrolysis. The technical problems of cellulose hydrolysis are to a great extend due to the fact that this is not the case. The lack of an adequate amount of chemical reactivity in cellulose is called lack of accessibility. This is related to the highly inert character and crystalline organization on a molecular level of the high molecular weight cellulose, and also the presence of lignin. Hydrogen-bonding almost certainly plays a very important role in the structure of cellulose, and may be a key factor in explaining its chemical inertness.
In general, mechanical treatments, such as, for example, intensive ball milling to sizes below 60 mesh, have been found to be technically effective, but at a high cost which renders any process economically prohibitive. Treatment with high-energy ionizing radiation on the order of 100 megarads has been shown to be effective, however the cost of such large doses of ionizing radiation is too high for industrial usage.
While heretofore successful batch-wise production of glucose from cellulose has been carried out by the acid hydrolysis of waste cellulose, this type of process and the apparatus for carrying it out are insufficient for commercial production.